Friday, January 21, 2011

Entangled En Masse: Physicists Crank Out Billions of Entangled Nucleus-Electron Pairs on Demand: Scientific American: With a series of radio-frequency and microwave pulses, Simmons and her colleagues set the approximately 10 billion phosphorus atoms in the silicon crystal into an entangled state wherein each atom was in a superposition of two states at once—both nucleus and electron in a spin-up configuration in one state, or both spin-down in the other. Measuring the spin of either the nucleus or the electron collapses the atom's superposition into one of the two possible states. "If you measure up on a given electron, you know that the nucleus is up," Simmons says. (The entangled state was not completely pure, so some atoms did not cooperate.)